STANDARDIZED UPTAKE VALUE AND QUANTIFICATION OF METABOLISM FOR BREAST-CANCER IMAGING WITH FDG AND L-[1-C-11]TYROSINE PET

The aims of the study were to compare the value of L-[1-C-11]tyrosine (TYR) and [F-18]fluoro-2-deoxy-D-glucose (FDG) as tumor tracers in pat ients with breast cancer, to investigate the correlation between quant itative values and standardized uptake values (SUVs) and to estimate t he value of SUVs for the evaluation of therapy. Methods: Eleven patien ts with one or more malignant breast lesions and two patients with one or more benign breast tumors were studied with TYR and FDG. Doses of 300 MBq of TYR and 230 MBq of FDG were given intravenously. All PET se ssions were performed using a Siemens ECAT 951/31 camera. Of 10 malign ant tumors and the 3 benign lesions, glucose consumption and protein s ynthesis rate were quantified. All lesions were studied using SUVs bas ed on body weight, body surface area and lean body mass, with and with out correction for plasma glucose or tyrosine levels. Results: All mal ignant tumors were visualized with both FDG and TYR, but the visual co ntrast was better with FDG, Increased uptake of the tracers was seen i n patients with fibrocystic tissue and complicated the visual assessme nt and the outlining of tumor tissue. Uptake in fibrocystic disease wa s more prominent with FDG than with TYR. No difference in tumor/nontum or ratio between the two tracers could be established. FDG showed a fa lse-positive result in one benign lesion. No major differences between the SUVs as defined above were found, although the best correlation b etween glucose consumption and the SUV was observed when the SUV was b ased on body surface area and corrected for plasma glucose level (r = 0.85-0.87). The SUV based on lean body mass was found to correlate bes t with protein synthesis rate (r = 0.83-0.94). Conclusion: in this gro up of patients, TYR appears to be a better tracer than FDG for breast cancer imaging, because of lower uptake in fibrocystic disease, SUVs c orrelate well with quantitative values, but future studies must determ ine whether treatment evaluation is also reliable with SUVs.